How do i make an "flashing color" with blend mode?

Hi i watched a video and i liked a effect very mouch. I wanna know how you make color come up on each corner while your changing color with blend mode ( background visible ) I will show you an example of an gaming video here is the link m.youtube.com/watch?v=LhFoTzH72PA. If you watch this video you can see color comming up and dissepearing and sometimes it even change color before it dissepear. I would be really happy if someone teach me how to do that for improving skills and personal use.

Thanks man for answering me. I searched up light leaks tutorials on youtube but i wanna know how i do it by myself cause all the tutorials is plug ins you need to download. Is it hard to do it by yourself?